21^st Century Astronomy, Second Edition

Chapter 13: Taking the Measure of Stars

Study Plan

To even the most powerful of telescopes, a star is just a point of light in the night sky. However, by applying our understanding of light, matter, and motion to what we see, we are able to build a remarkably detailed picture of the physical properties of stars. As we take this first step beyond our local Solar System, we will

• Apply a form of "stereoscopic vision," extended by Earth's orbit, to measure distances to nearby stars.
• Use the brightness of stars and their distances from Earth to discover how luminous they are.
• Use our knowledge of thermal radiation to infer the temperatures and sizes of stars from their colors.
• Classify stars, and organize this information on a plot of luminosity versus temperature, called the Hertzsprung-Russell or H-R diagram.
• Measure the composition of stars from spectra.
• Discover that 90 percent of the stars we see lie along a well-defined "main sequence" in the H-R diagram.
• Study the orbits of binary stars and use Kepler's laws to calculate their masses.
• Discover that the mass and composition of a main sequence star determines its luminosity, temperature, and size.
• Explore the range of stellar properties, learning how our Sun compares to other stars.

Organize

1. Read Chapter 13 in your textbook or ebook.
2. Take the Diagnostic Quiz to assess your understanding of the basic concepts and identify gaps in your understanding of the assigned reading.

Learn

1. Access the Animations given for this chapter. These brief lessons enhance your understanding of core concepts.
   Solar Spectrum
   Section: 13.3
   H-R diagram
   Section: 13.5
2. Use the FlashCards to test your memory for new terms.
3. Review Foundations Box 13.1 on Spectral Type and Box 13.2 on Using a Celestial Bathroom Scale to Measure the Masses of an Eclipsing Binary Pair.
4. If your instructor has assigned SmartWork online homework, login from the right navigation pane for additional practice and review.

Connect

1. Periodic Connections boxes and the Seeing the Forest through the Trees section at the chapter's end draw your attention to recurring themes and help prepare you for concepts explored more fully in subsequent chapters.
2. Visit Astronomy in the News for breaking news of new discoveries and the opportunity to apply what you've learned in this chapter to real-world (and real Universe) events.

Instructors now have an easy way to collect students’ online quizzes with the Norton Gradebook without flooding their inboxes with e-mails.

Students can track their online quiz scores by setting up their own Student Gradebook.